I recently picked up a Scat Trak 530 mini excavator with pilot controls. The machine runs great but has hydraulic control problems. The problem is the boom, bucket, and crowd operations are slow or barely work, unless you operate a function on the opposite joystick at the same time. The left side drive track is stuck but the right seems to move as long as you are operating another function. It appears the control block is divided into three segments. One being, turntable, blade, and offset boom (This group works fine). Second being Right track, bucket, and aux, and a third being boom, left track and crowd. When you try one function all by it self it sounds like a relief valve is opening, not sure which one, port or main relief. I have checked the three main reliefs to see if they are stuck and they appear to be in working order. I have also moved the relief from the working circuit (Blade and offset boom, and turret control) but that did not have any effect on anything. The guy I bought it from had the pumps tested and they are within spec. All of the electrical solenoids are getting power and seem to be working. Any ideas on where to go next?
Does it have 3 pumps? Left track, right track and functions? Is there room to swap the lines from the left drive to right?
The right side track moves a little bit. The left side track does not move on it's own, but if you do perform another function at the same time the track will move a little bit. I just picked up the machine a week ago and I am just starting to dig into it. I knew it was a project when I bought it. One thing I forgot to mention is that the pilot controls are weaping fluid up in the cab. I am not sure if this is causing a pressure drop. I am going to do a fluid and filter change as I am not sure what fluids have been added to the machine.
sounds like quite a project, good luck drag a magnet along the bottom of the hydra tank and see what it picks up.
I've never even seen a Scat Trak excavator in my area, much less worked on one. Your describing things I've never even heard of. My first thought would be a problem with a dual chamber hyd pump, but I don't know if it even has a dual chamber pump, and you stated the pump was tested and checked OK. It doesn't make sense that it would be a pilot system pressure problem, else it wouldn't work by operating a function on the opposite joystick. I can't see how it could be a relief problem because you stated that if you get into a single function, it sounds like it's opening a relief, but again, if you operate a function on the other stick the problem function works OK. Does your pump have "load sensing" hoses going to it, or does it sense the load internally at the pump. You stated boom, stick, and bucket are slow working alone. Are they slow in both directions, up/down, in/out, curl in/roll out? Just tryin' to get a little more info because I have no idea what's going on at this point.
Hydraulic Problem With Pilot Controls: This is a total guess, but it almost sounds like somebody might have tried to change the pattern and hooked the pilot hoses up wrong. Especially when you state that the pilot controls are weeping fluid up in the cab. Take the boom for example... you try to raise it and it sounds like a relief is opening, which it might be, possibly because the return port is hooked to another lever, and when you activate the other lever, the return port opens and it seems to work. Again, just a guess, and I don't know if it even works that way, but it sounds like a conflict in the valving some where. OCR
The machine has a triple gear pump, and it does not appear to have load sensing hoses going to it. The functions that work all the time are the dozer blade, offset boom swing, and house turntable. The turntable is the only thing on this circuit that uses the pilot controls, the others are purely mechanical spools with linkages. I have been trying to figure out why these work all the time. These circuits do not have port or antishock vavles like all of the other circuits, I am not sure if this matters. Just giving some additional information. I guess its possible the hoses could be wrong going to the pilot control. I will have to double check the routing. I am waiting to get a hydraulic filter so I can eliminate that, and I will try to get to the in tank filter to clean it. I keep thinking about a clogged filter, but it would not make sense that the dozer blade circuit would work fine and the others would not. I appreciate everyone's comments so far. I look forward to hearing any further suggestions.
Are you for real about that? Triple gear pump? Man, I said I haven't worked on one...and I wouldn't have dreamed of that on an excavator, even a small one! If it has gear pumps, there wouldn't be sensor lines to the pumps, but I would just about bet that it's a closed center hyd circuit. With gear pumps, this would require some kind of load sensing valving to dump oil from the positive displacement pumps when oil is not needed, I guess you could call it differential sensing. JLG and Genie uses gear pumps on closed center circuits with these type of sensing valves, but I have no clue what Scat Trak is doing on this excavator. But I'm still curious what's causing your problem.
Yes, it is a triple gear pump. Is this a good or bad thing? I bought a manual for this machine. It is not a factory manual, but more like a translated manual from Italtian to English. The machine is the same as a Libra excavator which I have heard is some sort of mining equipment manufacturer in Italy. After looking at the hydraulic circuit I have discovered that there is a high power circuit that is engergized by a solenoid. When engergized redirects return flow from from circuit 1 (Which is the dozer blade, swing, and slew) to the other two circuits. This is currently how the machine is running in high power mode. When power is shut off to this circuit flow from circuit 1 goes back to the tank. With the solenoid off the machine barely moves except for the functions on circuit one. They still work all the time. Maybe the second and third segment on the pump are not working? I am starting to move away from it being a pilot control problem for now. I am wondering if the system is not getting flow from the tank. I am going to drain the hydraulic tank and try to clean the suction filter, and replace the inline filter to see if that helps. All I need is for it to stop raining.
Scat track pilot issues I have a scat track 224s, I'm having simialr issues. I did find out the the machines are still being produce in Italy as Libra units and that the Vermeer factory can and will still get parts for them. I just got the Hyd. schematic for mine today and have begun sorting through it. Assuming they are a bit the same I have a 3cyl. Kubota coupled to a Nachie variable displacement piston pump with (2) discharge ports, behind that is a a gear pump. The piston pump apparently has an internal circuit that destrokes the pump's swash plate at about the same time the relief pressure is met. I found this by attaching a flow control valve and gauge to the discharge ports one at a time and slowly began closing the valve to see if the pump loaded up and built pressure. (the other end of line I just ran into the tank through the filler cap) Mine is also plumbed to the control valves in three segments with (2) solenoid operated valves marrying the pumps together for additional flow, this is controled in the right stick with two buttons one on and one off. If you look at the schematic there is a block that has two solenoid valves and an accumulator on it. One of the solenoids gives you high speed travel and the other shuts the pilot oil off if the left armrest is lifted. I'm not there yet but I think the problem is in that valve block. It has two different control pressures one is 35 Bar and the other is 50 Bar. There is a check valve between the accumulator and the 35 bar test port (m-1 on the schematic) I'm not yet certain but somthings fishey there. Please keep me posted as to your progress and I'll do the same, maybe we can help each other. I can't help but thinking we are not the only two to have had these problems. I'll continue to try to find a mechanic that is familliar these machines as I'm begining to believe this may be a fairly common problem. My machine came from H&E, it was a rental unit. I have limited connections with H&E as the outfit I work for buy's Krupp/Grove AT cranes from them. At the present one of there guy's is trying to find out wich store my machine came from in the hopes and can find out who may have worked on it the past. Anyway good luck and I hope to hear from you soon. Best regards, George
Wow, this is getting tangled, one has gear pumps...one has piston! Gear pumps are neither good nor bad here...just different. Most (in general) excavators use piston pumps and closed center hyd circuits. It would just be not the norm if yours had gear pumps. And if it does, I still think it would be a closed circuit system and have to utilize some form of differential sensing to control pressure output of the pumps. I'm thinking it's a problem of single pump output to a function not working properly, then when you combine flow from multiple pumps via valving, you get a reaction. That's still a vague longshot at this point. And I would be curious that the pumps were, in fact, good. I learned a long time ago when wrenching on something, that if someone says "yeah, I checked that...", I'm going to check it anyway. I want to see it for myself. Is it possible for you to switch the pump output hose around and see if your problems move to other functions? Just a few thoughts.
Hello sdcraneman, and bremery, The gear pump that you refer to, could possibly be the charge pump for the variable displacement piston pump, I know they require some type of charge pump. That does seem to be a rather unconventional arrangement on bremery's system though. Keep us posted... a learning experience is almost always beneficial to every one. OCR
Hey OCR, I was already typing this on wordpad when I noticed you had posted. Here's a few thoughts I have about the pumps. sdcraneman, the arrangement you described on your machine is what is more common on excavators. A dual chamber piston pump to supply oil to work equipment. The gear pump that piggybacks off the piston pump provides oil for the pilot circuit. Many of these type of piston pump arrangements have internal load sensing and not sensor lines coming from valves to control pump output. Also, they don't necessarily "destroke about the time the relief pressure is met". Most of these load sensing pumps, whether piston or gear arrangements, are designed to maintain a set pressure on the system. When no functions are being used, this is what we commonly call "standby pressure". It usually ranges from 300 - 500 psi. To keep description simple, let's say 300 psi. The machine is running, your operating no functions, it's a closed center hyd circuit (which is a dead end), and the sensor circuit "destrokes" the pump to maintain 300 on the system. Now, you operate the boom. There is a pressure drop because oil is being demanded. The sensor circuit says "oh shoot, pressure went down!" It "strokes" the swash plate to deliver more oil because it's trying to maintain that 300 psi. But wait a minute, the boom requires more than a meager 300 psi to raise it doesn't it? That's right. That's where "pressure differential" comes in. The sensor circuit is always trying to stay 300 psi above what is demanded. Let's say when you operated the boom, it required 1,000 psi of pressure to operate it. At that point, the sensor circuit will adjust pump to deliver 1,300 psi of pressure. 300 lbs above what is demanded, pressure differential. Gear pump arrangemnents can do this as well, but in a slightly different way since they can't "stroke/destroke". Gear pumps, or positive displacement pumps, produce flow constantly. When no functions are being used, and it's a closed center circuit, that pump is going to produce oil flow. Something's going to blow! So you commonly will have some form of differential sensing valve that dumps oil from the pump back to tank, except for that magic 300 psi. It just holds it there. When you operate a function and oil is demanded, the valve closes the dump line and lets the oil go to the function selected, and again maintains 300 psi more than is demanded, excess is dumped to tank. Well, that's the nuts and bolts of the pumps, now we just gotta figure out which component has decided to be the problem child in this three ring circus.
Hydraulic Problem With Pilot Controls: Man ATCOEQUIP, That description was way better than you can get from most tech manuals. Good'un... :thumbsup OCR
Thanks guys, I thought the gear pump was probably a charge pump also. The stange thing is, it is plumbed into the control valve on The end I believe. The 2 ports on the piston pump are set up to feed the center and the opposite end. I didn't see any plumbing that even feeds charge pressure to the piston pump. I was thinking that maybe it is internally ported?? The gear pump gets it feed oil from internal ports in the piston pump as there is only one feed line 2-1/2" that goes into the piston pump. I will tell you that the tank is high than the pumps by a bunch, lubrication by head pressure??? I wouldn't think so but I'm just not sure and the schematic isn't that detailed. Thanks again guys, with your help I'm sure we'll figure it out. Best regards, sdcraneman
Craigslist project #???? Least I didnt have to come over with the backhoe this time to unload it......... I knew you couldnt resist buying it, I saw it hiding out back, haha.
Well, I'm just a High School edjumacated hillbilly from East Tennessee. Sometimes, I have to take that high tech stuff in the manuals and translate it for myself so myself can understand what it said. Other times...I'm of all men most confused!
Yep, sounds like your gear pump is for pilot/control pressure, fairly typical. And the piston pump is fed by the higher tank level as well as most of these systems have about 15 psi of pressure at the hyd tank. You'll probably hear a hiss if you open a fill port on the hyd tank after you've run the machine from this pressure. It also sound like your describing a dual piston pump on your rig. You said your machine "has similar issues", give us a description of the things your machine is doing. At this point of head scratching, any info is useful from either one of you because we are not there tinkering with the machine.
I picked up some fittings and a pressure gauge today to check the pressures at the pilot control pressure reducing manifold. I plumbed the gauge into the port where the hoses come in from the valve block. I found out the three main relief valves were set high, so I adjusted these to what the manual said to. The dozer blade, offset boom and turntable is set to 190 Bar, and the other functions are set to 210 bar (My hydraulic circuit diagram shows them all being 190 bar, which is a little different than what the procedure says). At full throttle and moving nothing I get about 300 psi. When I move a single function the pressure jumps up to what I set the relief at. I then moved the pressure gauge to port right at the pilot lines that go joysticks. I get little to no pressure at max engine rpm and no functions being operated. When I try a function the gauge will read 600-700 psi. The spec is 400 to 545 psi. This is a little high and I need to adjust this. I got it pretty close on my first attempt, but rain out of day light. I need to get a tee fitting to verify I am getting 500 or so psi to the spools. I also changed the hydraulic fluid and cleaned the in tank filter. It was pretty clean to begin with. I did not replace the main hydraulic filter as I got the wrong one from the parts store. I am getting the correct one tomorrow and will put that to see if that helps. After getting the fluid warm, the hoses get warm and the filter gets warm, but the return hose to the tank does not get warm. I am hoping my filter is clogged up. I believe my problem is still flow related, but I am running out of ideas. Someone mentioned pilot filters? Any ideas of where these could be and if they can be troublesome? What about air in the system? Can that cause airlocks? Can it be bleed. Thanks for everyone's help so far.
I sure would like to see the schematics on these machines. I kinda clueless without them.
Hydraulic Problem With Pilot Controls: Here's a quick test you might try, if you can see your hoses, while you engage a function. If boom up is causing a relief to squeal, try booming up and watch the boom hoses. If they both swell up or jerk a little, that would indicate a block in the return, at or in the return port. Try this on any circuit that seem to open a relief and watch the hoses. Can you trace all main hoses to the the correct valve port? Do you have any quick couplers on the affected circuits? Affirmative. OCR
Here is a link to a copy of the hydraulic circuit from the service manual. http://www.bremery.com/530/530_Hydraulic_Circuit.PDF
Wow, I haven't seen an excavator circuit like this one before. Pretty interesting. Hey I see your problem already, the schematic shows you have two "left track motors"! Seriously, I'm studying it. Thanks for the link.
Have you checked the auger/hammer solenoid is not open ? If it is stuck or turned on , the machine will behave as you describe .
I'm not sure Iron Horse, what I'm seeing on the schematic is the aux valve is the dump line for pumps 2 and 3. The schematic is showing three positive displacement pumps, all of equal displacement. The circuits are open center valves, pump 2 and 3 circuit is dumped to tank via aux valve, pump 1 circuit is dumped to tank via solenoid valve. I'm trying to figure out what operates that solenoid that goes to tank on the P1 circuit, I'm thinking maybe high drive, but I've never seen it like this, because it appears it would give you high speed boom, bucket, and crowd as well. Haven't seen this before. Does the machine have high drive bremery?
Went back to review the thread, found this at post #9. This is exactly what I'm staring at on the schematic. Your problem could be the one way check valves at port P4 and Z (or 7, can't tell), seems crazy, though, because it would require failure of all 3 check valves. But I've seen crazy things before, and it would definitely cause your problem.
I didn't have much time today to work on the machine, but I did make some progress. I changed the hydraulic filter and it did not help. I did exercise the hammer circuit at the spool and it did not help. However, while holding the hammer circuit open I can get the non working functions working individually. Meaning I do not need to cheat and open another valve on another circuit, nor do I need to operate in "high power mode". I guess this is good news. I need to pull these two check valves out of the valve block. They appear to be in the valve block pretty tight, and little access to get a socket on them. It also appears that I have a stuck drive track. The lower rollers do not move. Will a little heat and penetrating oil work? Thanks for everyone's help so far.
I'm not sure what your describing. When you refer to the hammer circuit, are you referring to the aux circuit? And I'm unsure of "exercise hammer circuit" and "holding circuit open". Help me get on the same page with you. Also, what operates the high power mode?
Hydraulic Problem With Pilot Controls: bremery, or ATCO, A quick question: Is this Aux. valve circuit considered a "power beyond" circuit? OCR
Technically, I think you could consider it power beyond, because it get's it oil after the oil has gone through other valve banks. But it's unique to the other functions because the aux uses oil from both P2 and P3 combined. Boom, bucket, and left track uses oil only from P3, except in high power mode, where P1 oil is supplied as well. Right track, and crowd use oil from P2, except in high power mode. Boom, bucket, drives, and crowd never combine P2 and P3, the aux circuit does.
ATCO, Yes, the hammer circuit is the aux circuit. I exercised the circuit by moving the spool with the lever to make sure it was not stuck open or closed. It moves freely. High power mode is activated by a button on the right joystick. This activates a solenoid to redirect the flow from P1. I hope this clears things up.
Hmm, you got me scratchin' my head OCR, so I did a little research. I was incorrect. Actually, the function valves are power beyond. A power beyond circuit defined at insider secrets to hydraulics describes it this way; Power beyond - also called high-pressure carry over (HPCO), is a facility on a mobile hydraulic directional control valve that enables the pressure gallery to be isolated from the tank gallery and be carried over to an additional valve - usually another directional control valve. The boom, bucket, drives, and crowd do this by closing the open center tank port when you engage a valve, then diverts the oil, through check valve, into a galley that supplies oil to other valves as well, allowing operation of multiple functions at one time. Thanks for leading me to correct myself. :notworthy
Got it, just wanted to make sure that's what you were referring to. I think your problem is very likely a problem with the check valves directly below the P4 port on the scematic. If they are cartidge type valves, it's likely seal failure, but it could be failure of the check valve as well. This is a very simple hyd circuit, and failure of those check valves would cause the exact problem your having. But I am still studying to see if there's another possiblity given the symptoms you've described.
Hydraulic Problem With Pilot Controls: The hyd. system on my 750 dozer is similar. That is, a gear pump that feeds a valve bank. (simplified description) It also uses control pressure to open a "dump" valve, so oil doesn't have to run through the entire valve bank if no functions are in use... oil goes straight to tank from pump. (return oil) This is a typical stacked valve arrangement with through bolts connecting the individual valves. You can put a "power beyond" valve in the system, but it's necessary to plug a port some where in the other valves... as opposed to just stacking another valve on. Probably way off here, and I'd have to get the books out to do better. OCR
I hear ya OCR, that's what got me disoriented. I was working on the control valve of a Case 1840 once, and Case called the outlet port of the control valve going to the aux valve the power beyond port. Seems we have different uses/application of the same term from the wizards of smart that build these things. Hmmm.
Hydraulic Problem With Pilot Controls: Good!!... I can shut up now... ... :thumbsup OCR
Your slippin' OCR, you didn't notice I spelled "schematic" wrong. Gotcha!
Hydraulic Problem With Pilot Controls: Didn't want to embarrass an "Old Hippie"... :lmao Besides the only reason I caught the words you're reviering to, was when I ran ieSpell for my reply, it checked your PM too... (read carefully)... lol LOL... when that pop up came up, I though I was in for a rear end chewing or sometning... lol again. Life's full of surprises though, eh... OCR...
Ahh, you can embarass this ole' hippie, I'm good with that. Heck, it wouldn't hurt my feelin's if someone else figured out bremery's problem, it's all about gettin' his problem solved.
Pardon my ignorance, but are the check valves you guys are referring to contained inside the valve block? Meaning do I have to pull the all the individual block assemblies apart to get to them? Also, in normal power mode, when I try to raise the boom or curl the bucket, I do get flow through the hose from P4 to Z which indicates the check valves are not working. I pulled a few hoses off today and did see some black residue that could be the left overs of an o-ring. I also spent some time spraying the stuck rollers with oil to hopefully free them up. With the help from you guys I am slowly making progress.
First of all, there's no shame in asking questions when your seeking knowledge of something you don't know. Asking questions is one of the ways you learn. Two of the check valves in question are within the manifold. When you look at your schematic, notice all of the control valves and assorted goodies look like they're inside a rectangular box. The box is the manifold. That means anything you see within the box is inside the manifold. But now it could still be a cartridge type valve (like a relief valve in apperance), which you can remove from "the outside", but the valve is still technically "inside" the manifold. There is another check valve, one that is shown outside the box/manifold, the one that goes from the Z ??? port to the P4 port. Now that one should be an external valve outside of the manifold, mabey in-line in a piece of piping. Let me make sure I understand you. Are you saying that you could take the line loose from P4, leave the port open, lift the boom or curl bucket, and oil would come out of P4. If so, that definately indicates you have a problem with that check valve.
http://www.bremery.com/530/Control_Block.JPG Item A is a plug. Item B looks like it could be a check valve as it does have o-rings at the end. It did not seem hung up, but I did not look like it moves at all.There is one of these on each side of the function block. My manual does not have any drawings for this part. I could not snap a picture at the time, but I can attempt to get one if that will help. Item C is a port relief / anti shock valve for the left track. I am not 100% that I am getting flow from P4 to Z. I used a wooden dowel to listen to see if fluid was moving through the hose. Its not quite accurate. I will loosen the hose and see if it leaks. That seems like a more surefire way to check. I tried to pull the main check valve near Z but it did not budge. I need to come up with a better way to get at it. Its the long brass tube in the middle of the picture. http://www.bremery.com/530/check_valve.JPG
In that last pic you sent, is that the Z port with the inline check? If so, where does that hose go?
If the schematic is true to your machine, the check valves we're looking for should be in the valve section for the aux circuit. The schematic is fairly good, but I noticed one flaw that might confuse you if you were not familiar with schematics and symbols. The relief valves don't show the internal pilot lines that open them under pressure to shift the spool and dump oil to tank. Here's what the reliefs should look like. The "dotted line" indicates an internal oil passage of the valve, or, internal pilot. Dotted lines on a schematic usually indicate either an internal pilot line or control pilot lines. It looks like your machine has British Metric Pipe Inverted Flare fittings. My local hose shops have the fittings to make hoses, but they don't have plugs/caps for the fittings or fittings that the hoses connect to, like the fittings that are installed in the valves, so be carefull working with these fittings so as to not damage them.
This hose goes from Z to P4. As for the fittings my local hydraulic shop is well versed in BSP fittings. I always try to be careful with these things anyways. I guess the next step is to pull off all the hoses and pull the valve block to see what is happening in there.
Well, I guess I asked the question wrong, my bad. Have you got a good pic of the valve section where that hose connects to? That should be, as you said, the P4 port, and the checks should be in that valve section. They should be serviceable externally without valve section disassembly. Notice I said "should be", it would surprise me if you had to bust everything down.
Here is another shot of the control block. (Ignore the pile of paper towels). http://www.bremery.com/530/Control_Block2.JPG There is another greyish plug on the back side of the block. I assume these are the check valves. I also verified that I do get leakage at P4, when I crack the hose fitting open.
Looks like your in the right spot. I'd start pulling cartridges/plugs there and get a better look. Also, you could get leakage by cracking the hose at P4 because of flow from the Z port. You would have to take the hose loose and put a plug in it to prevent flow from the Z port.
I know the top one is a plug. The other one threads into the block and has o-ring seals on the end. It is the same on the opposite side of the block. I will try to snap a picture of it tomorrow. When I pulled it out a day ago, I did not get a good look at it.
Cool, pics are good! I'm thinking the plugs are where you would normally connect hoses for aux circuit and you don't have your aux plumbed. Like I said, "If" the schematic is true to your machine, those checks "should" be in that valve section. I'd pluck everything out of that section if I had to in order to find them. By the way, did that relief valve illustration I made make sense to ya?
I believe my machine is plumbed for one way operation for the aux circuit, meaning it will not run a double acting cylinder. I guess that is why its called the hammer circuit in the manual. The schematic does appear to be true to my machine so far. I pulled the fitting that P4 threads onto and it has nothing in it. It is an extension fitting and it is a clear pass through into the block for oil flow. My guess is the grey plug is one of the check valves. I really need to get a better look at them. Earlier someone mentioned the seals on the check might have failed. If the seals are the problem is it better to rebuild them or get a new check valve? I will also look at the check valve at Z. Thanks,
I don't suspect an issue with the inline check at this point. I've looked at the schematic, and actually don't see a point in that check valve being there except a redundant check in case the ones in question fail, then it would prevent unwanted oil flow from P2 and P3 over to the P1 circuit. Pull the goodies out of that aux section and we'll go from there.
Here is a picture of what I think is the check valve. There are two of these in the function block. If this is not a check valve, what is it?
Need a little more than that. Are there holes in the side of the vavle? What's the bottom of the valve look like?
The bottom is flat with no holes and there are no holes in the side. I expected it to look similar to this, but clearly it does not. http://www.nbhhyy.com/en/p_detail.php?id=31 The only other fitting on the aux block is the supply line to the boom. I guess this means I have check valves built internally?
No holes, it's not a check valve, it's some sort of plug. But even a plug, if it has seals, has a purpose. I can't tell in the pic what the seals look like, they're kinda covered with oil. I'd go ahead and put a new o-rings on both of these plugs, you may be able to re-use the back up rings. You woldn't happen to have a parts book illustration that shows an exploded view of the valve sections would ya?
No luck on a diagram for this plug. It was tough to tell the condition of the rings, but they were not torn or nicked. Are there any other places the checks could be other than in the block? If not, I guess its time to take the hoses off and pull the control block out. The checks must be pretty small because the aux block is not that wide.
Bummer! :Banghead They don't necessarily have to be torn, age and heat causes o-rings to get hard and square, they no longer have the roundness and pliability to make a good seal and oil can leak by them. This usually makes a hissing sound, but it also usually causes failure of the o-ring. It's worth a shot to put new o-rings on it just to give it a try. Could they be somewhere else? Possible. It's just the schematic shows them located in the aux section. They could be inside the valve section body, but even then there would have to be a plug to access them. Cound even be underneath in the bottom of the valve section, I haven't seen that too many times though.
I will try replacing the o-rings. I bet there metric. It will take a few days to get them, unless my local hydraulic shop has something that will work. Some Buna-N / Nitrile 90 durometer rings will do the job. If this was a circuit for a dual acting cylinder, like the boom swing, there would be a port relief valve instead. Maybe these rings keep the flow from getting to the discharge port, and if the rings are shot the oil passes by them creating a hiss. I do get a hiss / squeal sound when I try to move a function like the boom under normal power. Sounds like a good place to start. Thanks.
Most cartridge o-rings are 70 duro, but 90 would work. The aux on this unit doesn't use port reliefs like other functions. If you look at the schematic, the aux uses the main reliefs. Your thinking what I was; these "plugs" are where port reliefs are normally located, and it's where the port reliefs are located on the other valve sections. Since it doesn't use port reliefs on the aux, they block the access to tank by installing the plugs instead of reliefs. And I would bet you can remove that plug on top of the valve section and connect your other aux line to it to have double acting, at least that's what the schematic is showing.
Problem With Pilot Controls: I know nothing... lol Oops, what I meant to say was; and it is hard to tell from the picture, but on some systems, they incorporate a valve to release the pressure manually, ie... engine failure, or something that causes the pilots to not function. My Cat 312 BL has this feature, it's called the "manual boom let down valve", or pretty close to that any way. I've never used it, but it's to let the boom down safely with no power. You actually have to climb up on the boom just a little ways to access it, and manually turn something with a wrench I think. I was going to expound on how it works, but that would be rather absurd without looking in the manual, because I'm not sure. Probably doesn't even apply to your situation any way bremery. On second thought, stick with the first line at the top... lol OCR... PS, that schematic is starting to look like this, and my eyes are going...lol
Yep, that does tend to happen.
I pulled the plugs out from the AUX block to measure the orings. I found one of the plugs was missing a chunk of the backup ring. It may be tough to see in the picture. I found replacement o-rings at McMaster Carr, but backup ring appears to be something special. I did order the closest backup ring I could get. The o-ring was standard and I did check to see if the backup matched up with anything metric, but I could not find anything close. The rings being worn might be a good sign in terms of getting closer to solving the problem.
Yeah, pic a little fuzzy, but you can see some damage. Bummer your only like 900 miles from me...I probably have the o-rings and back ups at the shop. :Banghead I believe I would pull everything I could remove on that aux section and look at every seal. Just don't bother pulling the spool, the only seals on it are seals at the outside to prevent leaking, unless you want to replace them as well.
Something strange is happening. I replaced the o-rings and backup rings on the two aux plugs. This didn't fix the problem so I pulled them out again. One plug was missing a chunk from the backup ring. I replace the o-ring and backup ring and tried again. This time the o-ring had a chunk missing from it. I stuck my finger into the bore to see if there was anything sharp in there. Also the plug went in pretty easy, so I don't think the threads are cutting the rings as they go in. Is it time the pull the control block out of the machine and see whats happening inside?
Are you certain the seals and backups are correct? The o-rings should only slightly protrude outside the diameter of a cartridge, or plug in this case, same thing. The backups should not protrude outside the diameter at all. Put new o-ring and back up on one, screw it in, then pull it out to inspect. Do it a couple of times if you like. If there's no damage, I think it's safe to say installation isn't the problem. It looks like in one of the pics there's a piece of iron above the valve body, is there any way you can get a good pic looking straight down on the top of the valve body?
Hmm were to start. The issues started with my machine some months back, Anyway the way it started was on ocassion the machine's functions would begin to slow down. If I raised the blade it would clear it up. I can't remember for sure but it seems like it would clear up as I began to raise the blade I don't think I had to dead head the blade in the up postion, as well if the blade was up I think I was able to lower it and get the same result. Then the problem developed and at times on start up it didn't want to work but by raising or lowering the blade it would go to work. The last time I used the machine I had run it all day long, shut it off. The next morning I lit it off and nothing, raised blade or otherwise. So far I haven't had a bunch off time to work on it but I put a set of test gauges on the block that controls the pilot oil and found it isn't seeing any pilot oil pressure. I remove this control block (the one with the solenoids and accumulator on it) and verified solenoid function by blowing air through it with 12v applied and removed. Air will pass through both ports, one is the high speed travel port, the other controls pilot oil feed to the control levers that shuts the oil off if the left armrest is lifted. The port for the armrest switch doesn't flow as well as the other and you actually have to hold your finger over it and partially block the port to get air to come through it. The other odd thing is I can't get the air to transfer from the where the oil comes in from the pumps to the pilot oil side. There is what I think is a double relief in this thing that I will attempt to describe. The schematic shows that the pilot oil port is normally open and is supposed to maintain 35bar. If I understand it correctly after it sees the 35bar it dumps the rest of it to tank. The pilot oil comes from a chamber in this block that is fed by all three pumps. There is a piston in that port that is drilled down it's center line. It is also cross drilled to line up with this oil fed chamber so the oil would travel down the center line in each direction. On one end it looks like a typical relief, it has a cone shaped plug followed by a spring, then adjusting washers held in place by a screw in exterior plug. On the other end the piston looks like it buts up against the check ball that traps the accumulator pressure in the pilot oil circuit. The side that has the cone shaped plug is the side where the oil returns to tank. I will sketch a dwg. and include the schematic and post it asap. Your help is greatly appreciated as this stuff is no my cup of tea. bremery sent me a schematic of the control lock that is excellent and I will include this also. Thanks in advance for all the help, Best regards, sdcraneman
You said in your first post that your machine had a variable displacement piston pump. Is that correct?
Yes it does, it has a Nachi PVD-1B-29P-9G-4690F. With a gear pump (maybe that's the 9G designation?) hanging off the back. The schematic shows a pilot line from each discharge port on the piston pump tied to the gear pump with what appears to be a counter balance valve or something. I guess this is what was explained in one of the earlier responses as to load sensing. I'm trying to get the schematic posted now so you guys can see it. The schematic actually shows two seperate variable displacement pumps, but the Nachi web site explains that it's two discharge ports with less than 1% differential between them.
Well, it took a little while but I have solved my major control problem. I still have some work to do to get it completely operational, but this is a big hurdle. I decided to take the whole control block out of the machine to really see what was going on internally. I discovered the check valves in the aux block at P4 were fine, and not clogged up. I did see that the internal checks (seen in the middle of the third picture) at P3 and P2 were installed backwards, preventing flow from the feed line from the pump. This machine came from an auction so my guess is something happened and someone tried to fix it and failed to put it back together properly so they sent it to auction. My trusty schematic pointed out the checks were preventing flow to the circuits. I put everything together (which sounds easy) and it works as it should. I now can move onto fixing some of the smaller hydraulic leaks and re-seal my leaky boom and bucket cylinders. Thanks for everyone's help. This place is a wealth of information and really accelerated the diagnosis of the problem.
Wow dude, nice work! :notworthy Yep, if those checks for P2 and P3 were installed backwards, that would disable the function valves unless you operated something on the P1 circuit. That explains the "hissing sound" you described...you were popping the relief when you operated a function. A schematic is invaluable when it comes to repairing a machine, it's the roadmap of how the machine works. And it helps fixin' screwups by wrenchbenders that have no business with a wrench in their hand...a shovel would be a better fit! Now we gotta figure out what's the problem with sdcraneman's machine. Might be better he start a new thread with for his machine.
Yeah, I was pretty shocked when I pulled the control block apart and saw the checks were backwards. It was the eureka moment I was looking for. I guess the only thing the prior mechanic did that was correct was that he labeled all the hoses for me. I just needed to write down where the went just in case I got confused in matching up the colors. To follow up on my previous post about the orings. I got the wrong size. They were tearing as the went in. Luckily I had some o rings from a previous project that were exactly what I needed. Thanks again.
Hee Hee! Sounds like your learning the wonderful world of o-ring seals. Most cartridge valves use ASA 568- o-rings. Occasionally, you'll run across metric, but it's rare on cartridges. Just have to ask to make sure; you are aware that the outermost o-ring on valves/fittings on your valve body is a Boss o-ring seal, meaning, 900 series o-rings. It's a different size than what you find in standard 568- o-ring kits and if you don't use 900- seals they will fail.
i have a scat trak 530. i think i had the same problem. I found out my valve that switches from deer to cat control was dropped down to the middle. I run mine on deer control which is up and the vibration lowered it into the middle and everything worked but not very well. I zip tied mine up and have had no problems since. That valve is on the right side (sitting on the machine) in one of those little access panels. I'm no machanic and you guys all know way more than I do, only hope this helps.
I was wondering if sdcraneman found the issue with his scat trak 224s. I have the same machine and have the same problem.
Having the same issue on a 224s I just purchased. Long shot considering the date on this thread but did you figure it out???
Pilot controls with gear pumps is weird...do u have pics of pumps? Could be as simple as low pilot/charge pressure
Currently in the shop. I tapped out. He said he wanted to start with testing each pump individually and then dig deeper. This machine now has a different pilot control relief value manifold installed on it. It is the one from Vermeer cx224. When I bought the mini it was half hooked up. We got it plumbed right except for the high speed travel hoses are now connected with a Tee on the relief valve. The original one had 2 separate holes for them. I have no clue if that is relevant or not. We'll see what the shop says and I'll definitely post updates...
Yep...that is a problem unless the tee is a shuttle valve tee...your pilot pressure is going back to tank instead of stroking the pump
Might be on to something. Totally not hydraulic educated but makes sense. I was wondering why there is only 1 port on vermeer part vs 2 on skat trak. Looks to be still same machine. Heck I don't even know why the previous owner bought the new part. I'm picking up blind where he left off... Thanks for the lead though! I'll keep you posted...
I was just reading my Cat 312BL service repair manual and it states in the first part of the hydrolic section that you must bleen the air out of the body / valve after changing the Hydrol fluid and filters. there is a simple hex nut on top of the block and you loosen that after turning off the engine and lowering the boom, and release the air. I am going to try this on my cat312 because it runs great everything fine except for i cannot turn right or left even on flat ground when its running. only when it first starts and is cold i can turn a little while driving. I also have no power climing a slight hill over 10% grade it just stops, no power in travel motors. I will check filters, hydrolic level and then will get pressure gauges, if any ideas let me know